For the first time in two years, Comcast (NSDQ: CMCSA) is reporting a positive quarter for advertising. “We’re not entirely out of the woods,” Comcast CEO Brian Roberts told investors and analysts during the cable operator’s Q1 call, but an increase of nearly 24 percent in its cable advertising revenue is a sign of a “real turnaround.”

It is a switch from the 15 percent overall ad decline for 2009, led by the auto category with signs of improvement in nearly every category and across local, regional and national — and, as COO Steve Burke pointed out — a “dramatic” change from the 23 percent ad rev decline in the same quarter last year. That’s $360 million for Q110, compared with $292 million for Q109. Burke said the last time Comcast reported growth in cable advertising was Q108.

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The turnaround was also reflected in higher advertising revenue for Comcast’s cable programming, up 6 percent for Q110 to $152 million from $143 million. The year-ago quarter showed an 8 percent decline. Burke attributed the increase to ratings strength and to general advertising improvements.

NBCU update: The ad shift bodes well for Comcast’s proposed deal with GE for control of NBC Universal (NYSE: GE), Roberts said. Midway through the process, he’s still “hopeful” the deal will happen later this year. Meanwhile, NBCU is costing Comcast money even before there’s a deal: this last quarter the company spent a net $14 million on the deal.

Other details of note from Q1:

— 3D: The consumer threshold for getting into 3D is lower than it was to buy into HD, Roberts said, but he doesn’t see it providing anything meaningful in the way of numbers “for a while.” Given that people have to wear special glasses, “I personally don’t believe people are going to sit there seven hours a day 30 days a month.” Insteads, think of it more as a “big event strategy” where people will watch something like the Masters, which Comcast just trialed in 3D, and movies or other live sporting events. Roberts also sees significant potential for broadband with 3D gaming.